Deflection system



Dec. 25, 1,9151 S, l, TQURSHOU 2,579,627

DEFLECTION SYSTEM Filed June 22, 1950 F' O. f/d

2 SHEETS- SHEET 1 INVENTOR Jzmeon [mazz Dec. 25, 1951 s. l. T'oURsHou 2,579,627

DEFLECTION SYSTEM Filed June 22, 195o 2 SHEETS- SHEET 2 lNvEN-roR J'Imeozz I. .Tazztyozz tems.

Patented Dec. 25, 1951 DEFLECTION SYSTEM i Simeon I. Tourshou, Philadelphia, Pa., assigner` to Radio Corporation of America, a corporation of Delaware 16 Claims. i

The present invention relates to cathode ray beam denection systems and methods and more particularly although not necessarily exclusively to electromagnetic cathode ray beam deection circuits of the type employed in television sys- Ventitled Television Deflection Power Recovery Circuit by Simeon I. Tourshou, led April'30, 1949, issued as Patent No. 2,555,831 on June 5, y1951. Its utility, however, is to be no way construed as limited to such direct drive deiiection systems.

In virtually all cathode ray beam deflection systems employed in the electrical art it is desirable that some means be provided'for controlling the amplitude of cathode ray beam deflection. It is further desirable that the means used to control the amplitude of deflection be of such a nature as to not adversely aiect the wave form of the deiiection signal dening the cathode ray beam movement.

In television cathode ray beam deflection sys- 'tems such an amplitude control is usually referred `linearity in the saw tooth wave form of current passing through the deflectionyoke. This problem of width control versus linearity in television deflections systems is most prominent in electromagnetic deection systems of the direct drive type wherein the electromagnetic deflection yoke itself is placed directly in the anode cathode circuit of the deflection output amplier.

klt is therefore a purpose of the present invention to provide an improved amplitude control arrangement for cathode ray beam deflection systems.

It is another purpose of the present invention to provide a new and improved method and apparatus for controlling the deflection amplitude of electromagnetic cathode ray beam deflection systems in such a Way as to maintain the deflection wave form substantially unaected by changes in amplitude.

It is further an object of the present invention to provide a novel width control sysetmv for television horizontal deiiection systems which is particularly applicable to the electromagnetic direct drive reaction scanning type of deflection circuit. In order toA realize the above objects and features of advantage the present invention contemplates the use of controlled degeneration in the output stageof the cathode ray deiection system. More particularly the present invention as applied to a pentode type deflection output amplifier contemplates the use of a controlled degeneration means in the screen grid circuit of the output amplifler.- An enhanced and expanded range of amplitude control is further provided by the present invention through the use of a loss controlling circuit associated With the output circuit of the Ydeflection amplifier by properly combining and coordinating the actions of the loss controlling circuit and the controlled degeneration means. A wide range of amplitude control is made possible with negligible influence on the deflection Wave form.

The present invention as particularly applied to electromagnetic cathode ray deection systems employing screen grid type output tubes receiving deflection signal drive from a multi-vibrator type deflection signal source contemplates the use of a novel and frequency stabilizing circuit. This stabilizingvcircuit in accordance with the present invention comprises a frequency control means for the multivibrator which in turn is actuated or 0 controlledby the degeneration means of the output amplifier. In this way changes in deflection amplitude have a negligible effect on the frequency'of the deflection signal.

In orderto more fully appreciate all the novel features of the present invention in additionA to those set'forth above, as well as obtain a more complete understanding of its nature and operation, reference may be made to the following description taken in connection with the accompanying drawings in which: ,g

Fig. A.1- is a combination block and schematic representation of one form of the present invention as applied to a television receiving circuit.

Fig. 2 is a graphical representation of certain l1947. '-'flection Circuits for Cathode Ray Tubes by AOtto H. Schade appearing in the RCA Review L for September, 1947 describes even lanother typical magnetic deflection circuit to which the aravaca? 3 characteristics peculiar to the novel operation of the present invention.

Fig. 3 is a combination block and schematic representation of another form of the present invention as applied to a television type deflection circuit.

Fig. 4 is a further modication of the present invention as applied to a typical cathode ray beam deflection circuit.

Turning now to the drawings there is shown in Fig. 1 a television receiver section I0 adapted to amplify and demodulate signals intercepted by the antenna l2. The output of the television receiver section l is made available at output terminal I4 for application to the grid of the Yimage reproducing kinescope shown at I6. A

portion of the demodulated signal is also made" available for the synchronization pulsev separator circuit I8. The separator circuit I8 delivers vertical synchronizing information to the vertical deiiection circuits 20. The separator circuit I8 also provides synchronizing information to the horizontal deflection generator 22. The output of the vertical deection circuit is indicated for. application to the terminals Y-Y of the deiiection yoke 24 associated with the kinescope I5. The horizontal-dellection signal generator 22 is by way of example illustrated as being productive of saw tooth type deection drive wave form 2c generally found in television deflection circuits.

Typicalk circuit arrangements suitable for application in the block diagram representations Ythus far discussed may beY found in an article entitled Television Receiver by A. R. Wright,

appearing in the March, 1947 issue of the RCA Review. Y

The -horizontal deflection amplier of the arrangement in Fig. 1 is based primarily on the .discharge tube 28. By way of example, this tube has been shown as being of the screen grid variety. Thedeection signal 26 is applied to the .control grid 30 of the output discharge tube. lThe cathode 32 of the Voutput tube is convention- -ally connected with ground through the cathode fresistor 34.

Resistor 34 is by-passed by capacitor 36 so as to` reduce `degeneration in the cathode circuit.V By wayof example, the anode 38 of the discharge tube 28 is connected with .the winding r11- of deflection yoke 24 rthrough a ydirect drive type deflection circuit employing B boost power recovery, reaction scanning action. The precise form of deflection circuit with which the output tube 28 is connected is not ofim- Aportance to the successful V,operation of the present invention, however, the direct drive type de- .ection circuit has been illustrated since the .problems overcome by the present invention are perhaps most prominent in this type ofdeflection circuit. Other types of deflectioncircuits l which may be connected in the anode circuit of tube 28 are shown and described in an article entitled Television Deiiection Circuits by A. W. Friend appearing in the RCA Review for March,

Another article entitled Magnetic Depresent invention nds ready application.

The direct drive deflection circuit shown in Figure 1 comprises a connection from the anode 38 of discharge ltube 28 to the primary of the 4 ondary winding 42 of this transformer are rectified by the high voltage diode 44 to produce beam accelerating potential for the kinescope second anode terminal 4B. The lower extremity of the primary winding on transformer is then connected with the horizontal deflection yoke winding 49 of the deflection yoke. From the lower end of the;deflection yoke winding a capacitor 50 is connected to the upper end of the variable linearity inductance 52.' The lower end of the inductance 52 is connected to the -l-B power supply terminal at 54 and additional capacitor 55 is connected from the lower end of the winding 48 also to the positive power supply terminal 54. Detailed description of the operation otthis circuit is described in the above identified U. S. patent application. A further description and disclosure of this circuit and its high voltage step` up transformer 40. Deflection fly-back pulses appearing across the secoperation may be found in the RCA Service Notes on Television Receiving Models T164, TC1664TC167, and TC168, iirst edition dated March 10, 1950.

Briefly, the discharge tube 38 is biased by some means so that under normal operating conditions the tube 28 conducts only during the positive going extremities of the saw-tooth 26. This bias may be obtained through the use of a bleeder resistor such as E6 connected between a source of positive potential at terminal 58 and the upper end of cathode resistor 34. Such bias conditions cause a saw-tooth of current to start building up in the yoke of the winding 48 during the latter portion of the saw-tooth 26. As soon as the retrace portion of the saw-tooth occurs an `oscillatory ringing starts in the winding 43. This is damped by the diode 60 to cause a saw-tooth of current to commence owing in the yoke 48 in the opposite direction to that produced by the peak of the saw-tooth 26. By properly adjusting the bias on the tube 28 and the amplitude of the signal 26 a quite linear saw-tooth of current suitable for deflection purposes may be produced through the winding 48. The above operation is predicated upon the supi ply to the screen electrode S2 of a suitable positor 58 and in part by the capacitor 10. In further accord withl the present invention the resistance tis made variable. The time constant of the resistor 64 with its associated capacity should be such that when resistance tt is adjusted to be zero the time constant in the screen circuit is substantially greater than the recurrence frequency of the deection wave form 26. Furthermore, the capacitor m is made large enoughrso that when resistor @6 is made substantially equal to zero the screen grid 62 is. eS- tablished at practically A. C. ground potential at signal frequencies corresponding to thedeection wave form. That is to say, the capacitor 'I0 is made large enough to offer a very low impedances path to deflection signal components.

. Under such conditionskthat is with resistance 65 equal to zero, the deflection circuit will operate in va somewhat conventional manner and will produce maximum deflection amplitude. Linearity of the wave form under such conditionsinay be' adjusted by varying the ance 52.

According to the present invention, if it should be desired to reduce the amplitude of deflection wave form, the tap 'I2 on resistance Sti is moved to the right so that both anaccelerating and a D. C. voltage drop will occur across the resistance GS. Since resistance 60 is not completely bypassed, this accelerating voltage drop will produce screen grid degeneration. The eiects of introducing screen grid degeneration in this manner may be illustrated by the graphical curve of Figure 2.

The graph of Figure 2 shows a plot of screen current versus screen voltage of tube 28 for various control grid-cathode voltages. Three such curves are shown'at i4, i6 and i8, respectively. Curve 'is depicts the screen current versus screen voitage characteristic for a control gridcathode potential of zero volts. Curve 'iS shows the characteristic for a control grid-cathode voltage equal to some nominal value E. Curve I8 illustrates the screen characteristics of the tube for a control grid-cathode voltage which is sufficiently negative to establish cutoff in the tube. Thisl value of voltage is indicated as ENC referring to non-conduction in the tube. With the resistance 66 equal to zero virtually no A. C. impedance is imposed in the screen grid circuit so that a deflection drive wave form such as 25, which is of sucient amplitude to drive the control grid from zero volts to ENC, will produce a screen current variation which is indicated by the vertical distance between points 80 and 82 on the ordinate of the graph value of A. inductin Figure 2. This zero impedance condition as stated before, corresponds to the maximum deflection amplitude producible by the circuit and may be referred to as maximum width. It is, of course, understood that the vertical line 86 corresponds to the average D. C. screen voltage. The difference between this average value and +B represents the D. C. voltage drop across the resistor 64. n

Should now, still looking at Figure 2, the resistance t be given some nite value the screen voltage uctuations will be defined by some load line such as S6. The slope of the load line 86 will be made to correspond to the actual resistance 50 as well known in the art of graphically analyzing vacuum tube operating characteristics. Under such conditions the same given amplitude of deection drive by the wave form 2S will still produce a control grid voltage change from zero to ENC. However, now the resulting screen grid current fluctuations will be much less than before and may be indicated by the vertical distance between point 88 and 90 on the ordinate of the graph in Figure 2. This has been arbitrarily indicated as being the screen voltage variation corresponding to minimum width. Since plate current fluctuations are a function of screen current changes in a -pentode it is clear that changing the valueV of resistance 60 will produce similar changes in the amplitude oi actual yoke deection current.

It is of importance to note that although in the prior art degeneration has been employed to control the amplitude of deiiection produced by vacuum tubes nowhere in the prior art has controlled degeneration been employed in the screen grid circuit of a -pentode The method of control provided bythe present invention is advantageous since the degeneration imposed does not alter the effective drive to the discharge tube 28. As Well known by those familiarwith deilection circuits, changing the eiective drive to a reaction scanning type circuit causes noticeable changes in the linearity of the resulting deflection. In the present invention, however, the effective control grid versus cathode voltage iiuctuations or driveremains constant and hence changes in the linearity of deflection current are minimized.

In still further accordance with the present invention a greater range of amplitude control may be obtained yby carefully controlling the losses in the reaction scanning deflection circuit during the control of degeneration in the screen grid circuit. Whereas prior art attempts to control deflection amplitude byV adjusting losses in the reaction scanning circuit have been successful to a degree, the range of such control has been limited by the resulting deflection wave form distortion when circuit losses were made too high. According to the present invention, however, by properly introducing the correct amount of degeneration in the screen grid circuit it is possible to realize an increase in the amount that deflection amplitude may be usefully reduced by applying losses in the reaction scanning circuit. This synchronized action of imposing circuit losses and degeneration may be accomplished by the convenient arrangement shown in Figure 1. Here the resistance 66 is a portion of potentiometer. The right hand end 02 of the potentiometer may be connected through the switch 94 to resistance 96. The right hand extremity of resistance 06 is in turn connected to the upper end of inductance 52. Withl .the switch closed the inductance 52 is fully shunted by a variable resistance whose value-may be adjusted by positioning the potentiometer arm 16.

Operation of the present invention in this regard is substantially as follows: As the arm 16 is moved to the right in Figure l an increased amount of degeneration is imposed in the screen grid circuit. At the same time the inductance 52 is shunted by a lower value of resistance. This increases circuit losses in the reaction scanning system and, therefore, reduces the eiiiciency thereof. This results in a reduced amplitude of deflection. As pointed out above, the increased degeneration also produces a further decrease in the amplitude of deflection. This compound control is not aggregative in nature since, as pointed out above, a wave form com pensating inuence is involved.

' The embodiment of the present invention shown in Figure 3 is in some aspects similar to that shown in Figure l. The same type of direct drive reaction scanning circuit is shown in FigureV 3 as was'indicated in Figure l. Here, however, the output tube 98 has its screen velectrode ,|00 supplied with bias through a somewhat diierent configuration of variable impedance from that shown in Figure l. Here the screen gridA |00 is connected with +B potential at 54 through two resistance paths. The rst path comprises resistance |08 in series with resistance l2; The second path comprises resistance |02. With the tap arm |04 of the potentiometer |06 moved to the upper extremity of potentiometer resistance a minimum resistance is imposed in series with the screen grid circuit. This resistance comprises the parallel combination of resistance |08 and resistance |02.` Capacitor ||0 is made sufficiently large under these conditions'so as to heavily by- .pass the resulting resistive impedance. Now, -as

the tap |04 is lowered on the potentiometer |06 an unbypassed resistance |2 comes into the picture. This imposes degeneration in the circuit and causes a reduction in deflection amplitude as was the case in Figure l.

The arrangement in Figure 3 further differs from that of Figure l in the following respect. Figure 3 indicates that the pentode 98 is being driven by a multivibrator type of sawtooth deflection wave form generator. This generator is of the time averaging type and is based on the dual triode H4. The first section ||6 of the dual triode ||4 operates as a timing comparator circuit so as to compare the incoming signal from the synchronizing pulse separator |8 with the developed saw-tooth appearing at terminal ||8. The resulting signal comparison produces a control voltage at terminal |22 of the cathode circuit of triode H6. Terminal |22 is' connected to the grid |24 of the second triode section |26. Triode |26 is further connected to operate as a blocking oscillator type saw-tooth generator. Thus, as the incoming synchronizing pulse signal is compared in time with the resulting saw-tooth appearing at terminals the bias on the triode section |26 is established to provide the proper operating frequency for the blocking oscillator saw-tooth generator. The feed-back transformer for the blocking oscillator is shown at |28. Its primary |30 is connected in the anode circuit of triode |26 while its secondary |32 is connected in shunt with the grid circuit of the triode |26 through capacitor |34. Positive potential for the anode of the triode |26 is supplied through the resistance |36 connected with a source of |B potential at terminal 54. The saw-tooth discharge capacitors |38 and |40 are connected with the upper end of the resistor |36. The saw-tooth developed across these capacitors is applied to the grid of the output tube 98 through a small resistor |4|.

The particular form of time averaging sawtooth deilection generator shown in VFigure 3 as a source. of driving signal for the output tube 98 and is of the general type shown and described in U. S.` application 136,021 led December 30, 1949, by Simeon I.v Tourshou entitled Beam Deflection Control for Cathode Ray Devices. A full description and operation of this type of signal deilection generator is also to be found in the January, 1950, issue of the Radio and Television News in an article entitled A Single Tube A. F. C. Circuit for TVl Deflection Systems by John A. Cornell commencing on page 58. According to these references the anode potential of the triodeI section 116' is made manually variable by means of a potentiometer sucl-il as |42 sothat a manual control of the deflection generatorA frequency may be had. In suchapplications the right end extremity of the potentiometer |42 wasv connected with a xed source of positive B potential. Thus, as the. value of theA anode potential ofthe triode H6 was changed the potential appearing atv |22. changed and the bias on the blocking oscillator triode |86 wasA altered. This, of course, caused a frequency change.

AccordingY to the present invention the right hand terminal of potentiometer |42- insteadY of being` connectedv to a fixed source of positive potential, it is connected to the4 lower extremity of potentiometer |96- associated with the above described reaction scanning circuit. The `following operation is obtained: When the degeneration control tap |04 is moved' downwardly along potentiometer |-06vthe degeneration inthe screengrid 8 `circuit of tube 98 is increased as disclosed bei fore. This degeneration reduces the effectiveness of screen grid |00 to shield the anode from the control grid of the pentode 98. Due to the wellknown Miller eifect this increases the effective grid-to-cathode capacitance of the pentode 98. Such an increase is effectively in shunt with the saw-tooth charging capacitor associated with blocking oscillator |26. The time constant of the blocking oscillator will therefore be increased. This will tend to reduce the frequency of the blocking oscillator'. However, in accordance with the present invention, the aforementioned movement of the tap |04 downwardly to increase degeneration has increased the potential applied to the anode of triode ||6. This will cause the terminal |22 to become more positive and apply a more positive bias to the grid of the blocking oscillator triode |26. As well known by those familiar with blocking oscillator action, this increase in positive bias wil-l tend to increase the frequency of the blocking oscillator and therefore tend to compensate for the increased Miller effect capacity imposed by the pentode 93. The parallel resonant circuit |44 connected in series with the anode circuit of the triode |26 acts as a further stabilizing influence on the blocking oscillator frequency as described in the above mentioned U. S. patent application 136,021 and Radio Television News article. The resonant circuit |44, of course, forms no part of the present invention.

It is to be understood that the novel frequency correcting action ofV the present invention is not limited to the preferred form of signal generator shown in Figure 3. For example, in Figure 4 a very basic type o blocking oscillator saw-tooth generator is indicated.. No means are provided for time averaging frequency control of the blocking oscillator by comparison of received synchronizing pulses with developed saw-tooth. However, in Figure 4, the triode |46 due to the action of the transformer |48 and grid time constant afforded by capacitor |52 and resistor |54 sustains periodic blocking oscillator operation. Saw-'tooth capacitor |55` charges substantially linearly through changing resistor lee during non-conduction of the blocking oscillator tube |46. During conduction of the tube |46, however, the capacitor |56 is discharged. This charging and discharge produces the conventional sawtocth wave form shown at |60. Such a blocking oscillator saw-tooth generator is shown and described in the above article Television Deflection Circuits by A. W'. Friend appearing in the RCA Review' for March, 1947. As well known by those skilledk in the television art the frequency of the blocking oscillator |46 is dependent upon the value of +B voltage applied to the circuit. The higher the +B voltage applied to the circuit the higher will be the anode voltage applied to the triode |96. This Will cause the tube |46 to reiiect a higher mutual conductance which will result in greater peak charging of the grid circuit It. C. combination. This of course will decrease the effective operating frequency of the blocking oscillator.

In accordance with the present invention the output pentode 99 in Figures. is connected substantially in the same manner shown in Figure 3 to provide variable screen grid degeneration control. Thus, in Figure 4, as the tap |04 is moved downwardly on the potentiometer element |06, the degeneration `in the screen-grid circuit of the tube 98 is increased. As described above this increases the effective*v Miller capacity-"in shunt With'thesaw-tooth capacitor i06- and lowers the frequency of the multi-vibrator. However, as the tap |04 is moved downwardly on the potentiometer H36, the D. C. voltage drop across the resistance section H 2 becomes greater and the anode voltage-applied to the blocking oscillator triode is decreased. As indicated above, this tends to increase the frequency of blocking oscillator I 4S and hence compensate for the increase in Miller capacityproduced by increased degeneration.

From the foregoing, it can be seen that the applicant has provided a new and useful width control arrangement for cathode ray beam deflection systems. It will be appreciated that although the present invention has been described in conjunction with electromagnetic type deiiection systems, its principle can be applied with advantage to electrostatic type deflection systems as well. Moreover, the novel frequency correcting action of the present invention, as shown herein, although illustrated in connection with blocking oscillator type saw-tooth deflection circuits, may be, of course, applied to other types of deflection signal sources whose frequency of operation may be controlled by altering circuit operating potentials.

What is claimed is:

1. In an electromagnetic cathode ray deflection system employing a deection yoke in combination, a source of deflection signal, an output tube having at least an anode, cathode control electrode and supplementary electrode interposed between said anode and said control electrode, connections for applying the output of said deection signal source to said control electrode, an output circuit connected between said anode and said cathode, said output circuit including means for coupling electrical variations developed therelin to the deflection yoke, a source of positive biasing potential havingk its negative terminal connected with said output tube cathode, an impedance having a resistive component connected between said supplementary electrode and the positive circuit of said biasing potential source whereby to introduce degeneration in the deflection system, a capacitor connected in shunt with at least a portion of said impedance to form a time constant combination, and means for varying the value of the time constant of said time constant combination such as to control the amount or degeneration present in said -system.

2. Apparatus according to claim 1 wherein said discharge tube is of the pentode variety and wherein said iirst and second control electrodes are respectively the control grid and screen grid of said pentode. v

3. In an electromagnetic cathode ray deflection system employing a deflection yoke in combination, a source of deflection signal, an output tube having at least an anode, cathode control electrcde and supplementary electrode interposed between said anode and said control electrode, connections for applying the output of said deflection signal source to said control electrode, an output circuit connected between said anode and said cathode, said output circuit including means for coupling electrical variations developed therein to the deflection yoke, a source of positive biasing potential having its negative terminal connected with said output tube cathode, a reactance connected between said supplementary electrode and the positive terminal or said biasing potential source, a capacitor "coniate electrode.

l'nected in shunt with at least a portion lof said reactance to form a time constant circuit, and Vmeans for varying the value of said resistance 4. In an electromagnetic cathode ray deflection system employing a deection yoke in combination, a source of deflection signal havinga predetermined period of recurrence, an output tube having at least an anode, cathode control electrode and supplementary electrode interposed between said anode and said control electrode, connections for applying the output of said deflection signal source to said control electrode, an output circuit connected between said anode and said cathode, said output circuit including means for coupling electrical variations developed therein to the deflection yoke, a source oi positive biasing potential having its negative ter'- minal connected with said output tube cathode, a variable resistance connected between saidsup'- plementary electrode and the positive terminal of said biasing potential source said resistance being variable between a high and low limitga capacitor connected in shunt with at least a portion of said resistance to form a time constant circuit the value of said capacitor beingsuch that the'time constant value of said time constant circuit is not substantially greater lthan the recurrence period of said deflecting signal when said variable resistance is at its high limit.

5. Apparatus according to claim '4 wherein said output tube is of the pentode variety and wherein said supplementary electrode is the screen electrode of said pentode.

6. In an electromagnetic cathode ray deilection system employing a deilection yoke in com.- bination, a source of deflection signal having'a predetermined frequency, an output tube having at least an anode, cathode controlelectrode and supplementary electrode interposed between said anode and said control electrode, connections for applying the output of said deflection signal source to said control electrode, an output circuit connected between said anode and said cathode, said output circuit including means'for coupling electrical variations developed therein to the deflection yoke, a source of positive biasing potential having its negative terminal con'- nected with said output tub'e cathode, a resistance connected between said supplementary electrode and the positive terminal of said bias source to form a supplementary electrode circuit, a capacitor connected in shunt with at least a por-.- tion of said resistance, the value of said capacitor being so related to the deection signal frequency and the Value of the resistance across which it is shunt connected that a degree of degeneration is produced in the supplementary electrode cir-'- cuit, and means for concomitantly varying both the degree of supplementary electrode circuit dez-r` generation so produced along with the value of potential applied to said supplementary electrode- '7. In an electromagnetic cathode ray defiecftion system employing al deflection yoke in combination, a source of deflection signaL'an output tube having at least anranode, cathode control electrode and supplementary electrode interposed between said anode and said control electrode,

connections for applying the output of said deiiection signal source to said control'electrode, an output circuit connected betweenrsaid anode and said cathode, said output circuit including antrace? -`means for coupling electrical variations developed therein to the deflection yoke, a source of positive biasing potential having its negative terminal connected with said output tube cathode,

means for applying said positive bias source to said supplementary electrode, means to produce degeneration in said output tube, and means for concomitantly varying both the value of bias potential applied to said supplementary electrode by said applying means and the degree of degeneration produced by said degeneration means.

8. Apparatus according to claim 7 wherein said varying means is so arranged that the amount of degeneration produced by said degeneration means is` inversely proportional to the magnitude of rvoltage applied to said supplementary electrode.

. 9. In a reaction scanning electromagnetic cathode ray beam deflection system employing a derlection yoke having in shunt across its winding a damping tube, the combination of a source of deflection signal, an output tube having at least an anode,Y cathode control electrode and supplementary electrode interposed between said anode and said control electrode, connections for applying the output of said deection signal source to said control electrode, an output circuit connected between said anode and said cathode, said output circuit including'means for coupling electrical variations developed therein to the deflection yoke, a source of positive biasing potential having its negative terminal connected with said output tube cathode, an impedance having a resistive component connected between said supplementary electrode and the positive circuit of said biasing potential source whereby to introduce degeneration in the deflection system, a capacitor connected in shunt with at least a Yportion of said impedance to form a time constant combination, an inductance connected in series with the shunt connections of the damping tube across the yoke winding, resistance means connected in shunt with said inductance, and means for concomitantly varying both the time constant of said time constant combination and the value of said resistance means whereby to control the amplitude of deflection signal applied to said deflection yoke.

` 10. In a reaction scanning electromagnetic cathode ray beam deflection system employing a deiiection yoke having in shunt across its winding a damping tube, the combination of a source of deflection signal, an output tube having at least an anode, cathode control electrode and supplementary electrode interposed between said anode and said control electrode, connections for applying the output of said deflection signal source to said control electrode, an output circuit connected between said anode and said cathode, said output circuit including means for coupling electrical variations developed therein to the deflection yoke, a source of positive biasing potential having its negative terminal connected with said output tube cathode, means for applying said positive bias source to said supplementary electrode, means to produce degeneration in said output tube, an lnductance connected in series with the shunt connection of the damping tube across the yoke winding, resistance means con nected in shunt with said inductance, and means for varying the following three entities simultaneously rst the value of bias potential ap.- plied to said supplementary electrode by said applying means, second the degree of degeneration produced by said degeneration means and third the value of said resistance means whereby to obtain versatile control of the amplitude .of deflection signal applied to said deection yoke.

1l. Apparatus according to claim 10 wherein said source of deleotion signal comprises a self excited multivibrator circuit having as part of its output circuit a sawtooth discharge capacitor where value denes in part the frequency of said multivibrator.

12. In an electromagnetic deection circuit for exciting the winding of a deflection yoke the combination of, an electron discharge tube having at least an anode, cathode, first control electrode and a second control electrode, means for applying a deection signal between said ydischarge tube first control electrode and said cathode, an output circuit for said discharge tube connected between the anode and cathode thereof, connections for driving the deflection yoke winding from signal energy developed in said output circuit, a source of biasing potential having its negative terminal connected with said dis.- charge tube cathode and its positive terminal connected with said discharge tube second ccntrol electrode, a degenerative network serially included in said connection to said second oontrol electrode, and means for varying the amount of degeneration produced by said degenerative network whereby to control the amplitude of deiiection produced by said discharge tube.

13. A cathode ray beam deflection system employing an electromagnetic deflection Vyoke in combination, a deflection signal source having output terminals, the vfrequency of the deiiection signal provided by said deflection source being a function of the electrical capacity imposed across said output terminals, an electron discharge tube having at least an anode, cathode and control electrode, connections applying the output ter.- minals of said deflection signal source between the control electrode and cathode for said discharge tube, an output ,circuit connected between the said discharge anode and cathode, said out.- Dilt circuit including moans for coupling cleow trical energy to Said. yoke, moans for varying the frequency of deflection signal developed by .scid deflection signal Source, controllable means for imposing degeneration in Seid electron discharge tube and coupling means connected between said frequency varying mea-ns and said controllable means.

14. Apparatus according to claim 13 wherein said electron discharge tube is of the screen variety and wherein vsaid controllable degeneration means is connected in the screen grid circuit of said discharge tube and wherein said coupling means comprises a connection from said discharge tube screen grid to said frequency vari ing means.

15. Apparatus according to claim 14 wherein said source of deflection signals is a multivibrator type sawtocth wave form generator having the saw tooth discharge capacitor in shunt with said output terminals.

16. An electromagnetic r.deflection circuit for exciting the winding of an electromagnetic deflection yoke, a combination of an electron discharge tube amplifier having aV screen grid, an input circuit and an output circuit, controllable circuit means connected to said screen grid for producing degeneration in said discharge tube amplier, means for coupling the deflection yoke Winding with said amplifier output terminals to form an output load for the ampliiier, means for controlling the loss in said load, said loss con-4 13 trolling means and said degeneration controlling being adapted to Work in synchronsm with one another.

SIMEON I. TOURSHOU.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,098,390 Iams Nov. 9, 1937 2,284,378 Dome May 26, 1942 Number 14 Name Date Packard Feb. 24, 1948 Schade May 4, 1948 Foster June 8, 1948 Schade Apr. 12, 1949 Torsch May 17, 1949 Bocciarelli Sept. 20, 1949 Trott June 6, 1950 Clark Jan. 2, 1951 Clark et a1 Jan. 2, 1951 Schade Jan. 2, 1951 Clark Feb. 27, 1951 

